Why are brake lights red ?

Why only red ? Why not blue, orange, purple, pink or any other colour ?
In case, if you think that red was the favorite colour of the one who had this idea (humour me) then you’re… WRONG !
Seriously, when the answer hit my mind I realised that – Yes, everything has a reason ! & the brake lights having red colour has a reason too !

Well, the answer is much of related to physics & behaviour of light & the article is also not gonna be too long but I am sure you will brag about it later because only few people know this & many of them would not have given a thought about that !

Red colour is a sign of danger & is a correct answer of the question but that’s just a logical answer(an answer to keep a kid’s mouth shut). So let us understand in the actual technical manner.

We are all familiar with the phenomenon of refraction. In simple words, refraction is just bending of light when it travels through one medium to another medium(rarer to denser or vice versa).


A great example of refraction & also a great example how nature fools us 😛 !

Back to childhood, when we learned the order of all 7 colours of a rainbow with the help of this name – VIBGYOR ! It wasn’t useful that time but now it is a bit. VIBGYOR is only a visible part of the Electromagnetic spectrum which can be seen by our eyes. Violet colour has highest frequency & red has got the lowest frequency in visible part of spectrum. Which also tells us that violet has got minimum wavelength & red has got maximum wavelength(since frequency is inversely proportional to wavelength). As the wavelength of violet is minimum, particles are able to disperse violet more effectively than red colour.

Since,                      frequency of violet    >    frequency of red
therefore,             wavelength of violet    <    wavelength of red
therefore,      deviation of violet colour    >    deviation of red colour.

Which gives us a conclusion that, violet deviates the most & red colour deviates the least which also means red coloured things can seen from greater distances. Light gets refracted due to moisture content in air, water(during rainy season), fog & the differences in the temperature of air which flows. No matter what, red light will travel the farthest than any other coloured light.
Braking is an emergency situation than accelerating your vehicle or any other situation. Hence, you see red colour is used for brake lights.

Red light can be viewed over long distances than white light (as white light is mixture of all the colours - VIBGYOR & so wavelength will average of all of these)

Red light can be viewed over long distances than white light (as white light is mixture of all the colours – VIBGYOR & so wavelength will average of all of these)

After all you read this, did it ring any bells ?
No ? Ok, I will tell you, also due to the same reason, traffic signals use red colour for stopping the vehicles.
It was first used by railroad industries since 1830s. This companies used a lighted means to let know the engineers when to stop & go. Where they decided to use the red colour to stop a train. Then this system was developed & used as traffic signal lights.

I guess you have realised that – Everything has a reason !


  1. So that’s why the red light district is so dangerous ☺

  2. Thank u for the knowledge…..its all about science.

  3. Thanks…..the information that you have give us is very good. I like it really.

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